The present invention generally relates to a graphite tube assembly for use in flameless atomic absorption spectroscopy and, in particular, relates to such a tube assembly adapted to cooperatively accept therein, at a preselected orientation, a sample holding platform.
During conventional atomic absorption spectroscopy measurements the graphite tube is placed in the path of a radiation beam and the sample to be measured is placed in a sample holding platform positioned within the tube but external to the path of the radiation beam. As well known the sample is then atomized and measurements are performed thereon. The sample to be tested is usually placed in the sample holding platform via an inlet port in the wall of the graphite tube.
It has been found, particularly when liquid samples are to be tested, that the sample holding platform is most advantageously oriented at a preselected angle from the center line of the inlet port. In addition, it has been found quite advantageous, in order to consistently achieve reliable results, to be able to exchange platforms, or remove and reinsert the same platform, while maintaining the same platform orientation with respect to the inlet port. That is, the preselected orientation should be the same for each platform inserted into the tube.
It is known, via U.S. Pat. No. 4,111,563, issued to Tamm, that the sample holding platform can be an integral portion of the graphite tube structure. While this may be advantageous to the maintenance of the preselected angle between the platform and the inlet port of the graphite tube, it has the disadvantage that the platform can not be exchanged or removed without destroying the graphite tube. Thus, if, for any reason, the sample holding platform has to be changed the arrangement in the above-referenced U.S. patent requires that the entire graphite tube be replaced.